"boardjunkie" wrote in message
...
I have an old Eimac 450TH xmitter tube I keep around my
shop as a
conversation item (I service pro audio gear). One of my
customers who
is well versed in the mfgr of vacuum tubes says it is not
really a
great idea to have it out in the open....possibility of
radiation. Any
truth to this? He said to put it in a box with some
unexposed camera
film for a while to see if there is any radiation
activity. I've never
heard of this and the envelope is still sealed as far as I
can
tell....there's no getter in these.

This rings a vague bell. The filiments used in this
tube, and very many other tubes is thoriated tungsten.
Thorium, in some forms, is radioactive. I don't know how
much thorium is in the filiments but I suspect not much. BTW
some lenses made shortly after the development of rare-earth
optical glass contain some thorium and are radioactive
enough to require some care. These are mostly some WW-2
vintage aerial photo lenses. Thorium glass has some
desirable optical properties but is eventually stained brown
by the radiation. There is a bit on these lenses on the web,
do a google search for radioactive lenses.


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Richard Knoppow
Los Angeles
WB6KBL